Multifunctional irrigation mitigates heat stress, delays sugar accumulation and preserves berry composition in cv. Sangiovese (Vitis vinifera L.)

Introduction: Climate change increasingly threatens Mediterranean viticulture, as rising temperatures, increased radiation and reduced precipitation impose multiple stresses on grapevines, negatively affecting yield and grape composition. In red cultivars, these conditions often lead to a decoupling between technological and phenolic maturity, resulting in wines with higher alcohol content, reduced acidity and lower color intensity. In addition, sunburn damage further compromises both yield and berry quality. To address these challenges, a multifunctional irrigation system combining post-veraison drip irrigation with evaporative cooling of the fruit zone was developed. Methods: The system was tested during the 2024 and 2025 growing seasons in a flatland vineyard of Sangiovese (Vitis vinifera L.) in Bologna (Italy), by comparing vines subjected to multifunctional irrigation (MI) with rainfed controls (RC). Vine physiological responses, yield components, sunburn incidence and berry composition were monitored during ripening. Results and Discussion: The MI treatment resulted in consistent reductions in both air and cluster temperature, complete prevention of sunburn damage, and improved vine physiological status. In particular, across both seasons, MI vines exhibited improved leaf physiological performance, as reflected by increased stomatal conductance and net assimilation rates, with differences becoming more evident under moderate to severe water stress conditions. A significant Year x Irrigation (Y x I) interaction was observed for total soluble solids (TSS). In the drier and warmer 2025 season, MI vines showed lower TSS and higher titratable acidity at harvest compared to RC, indicating a significant but slight delay in technological maturity. Although anthocyanin concentration did not differ significantly between treatments at harvest, MI vines exhibited higher anthocyanin concentrations during ripening while the multifunctional irrigation system was active. These findings suggest that the combined irrigation–cooling strategy may allow harvest at lower sugar concentrations while preserving anthocyanin concentration, potentially contributing to a better balance between alcohol content and color intensity. In conclusion, the combined irrigation-cooling strategy can mitigate heat stress, delay sugar accumulation, and preserve both phenolic composition and acidity. However, its effectiveness depends on seasonal conditions and water input, and further studies are needed to evaluate its performance under more severe stress conditions, such as hillside vineyards, where water and heat stress are typically more pronounced.